Chimney Swift

A bird best identified by silhouette, the smudge-gray Chimney Swift nimbly maneuvers over rooftops, fields, and rivers to catch insects. Its tiny body, curving wings, and stiff, shallow wingbeats give it a flight style as distinctive as its fluid, chattering call. This enigmatic little bird spends almost its entire life airborne. When it lands, it can’t perch—it clings to vertical walls inside chimneys or in hollow trees or caves. This species has suffered sharp declines as chimneys fall into disuse across the continent.

Measurements

Both Sexes

Relative Size

About the same size as a Cliff Swallow.

Other Names

Martinet ramoneur (French)

Vencejo de chimenea (Spanish)

Cool Facts

Before European settlement brought chimneys to North America, Chimney Swifts nested in caves, cliff faces, and hollow trees. Their numbers rose accordingly, but a recent shift in chimney designs toward covered, narrow flues are unsuitable for nesting and may be contributing to a decline in this species’ numbers. For information about a Chimney Swift tower made specifically for nesting swifts, you can visit the North American Chimney Swift Nest Site Research Project.

Chimney Swifts are among the most aerial of birds, flying almost constantly except when roosting overnight and nesting. When they do come to rest, they never sit on perches like most birds. Their long claws are suited only for clinging to the walls of chimneys and other vertical surfaces.

Swifts even bathe in flight: they glide down to the water, smack the surface with their bodies, and then bounce up and shake the water from their plumage as they fly away.

Large numbers of Chimney Swifts roost together in a single chimney during the nonbreeding season. There’s warmth in numbers: during cold nights, the temperature inside a chimney roost can be 70°F warmer than outside.

Unmated swifts continue roosting together in the summer, sometimes in large groups. But the species does not nest colonially: you’ll find only one breeding pair nesting in any one chimney. The pair may tolerate other nonbreeders roosting in their chimney.

The Chimney Swift uses glue-like saliva from a gland under its tongue to cement its nest to the chimney wall or rock face. Sometimes an unmated swift helps the breeding pair rear the young. The young outgrow the nest after about two weeks and have to cling to the nearby wall, in many cases even before their eyes are open.

The oldest recorded Chimney Swift was a male, and at least 14 years old when he was recaptured and released during banding operations in Ohio in 1970. He had been banded in the same state in 1957.

Habitat

Town

Chimney Swifts breed in urban and suburban habitats across the eastern half of the United States and southern Canada. They are most common in areas with a large concentration of chimneys for nest sites and roosts. In rural areas they may still nest in hollow trees, tree cavities, or caves. Chimney Swifts forage mostly over open terrain but also over forests, ponds, and residential areas. During migration they forage in flocks over forests and open areas and roost in chimneys at night. They spend the winter in the upper Amazon basin of Peru, Ecuador, Chile, and Brazil, where they are found in open terrain and on roosts in chimneys, churches, and caves.

Food

Insects

Chimney Swifts eat airborne insects. Feeding on the wing, they capture flies, bugs, bees, wasps, ants, mayflies, stoneflies, beetles, caddisflies, fleas, craneflies, and other insects. They grab large insects with their bills; small ones go right down the throat. Chimney Swifts feed over urban and residential neighborhoods, fields, grasslands, shrublands, orchards, forests, and marshes, usually some distance away from nest sites. They can also pick insects from branch tips and “helicopter” down through the foliage to flush out prey. Normally diurnal foragers, they sometimes hunt for insects at night around streetlights or lit windows. They have been reported taking berries from elderberry bushes.

Nest Description

The nest is a half-saucer of loosely woven twigs, stuck together and cemented to the chimney wall with the bird’s glue-like saliva. Both parents independently contribute to the nest: they break off small twigs with their feet while flying through branches, then return to the nest site with the twigs in their bills. The completed nest measures 2–3 inches from front to back, 4 inches wide, and 1 inch deep.

Nest Placement

Building

Although they originally nested in natural sites such as caves and hollow trees of old-growth forests, Chimney Swifts now nest primarily in chimneys and other artificial sites with vertical surfaces and low light (including air vents, old wells, abandoned cisterns, outhouses, boathouses, garages, silos, barns, lighthouses, and firewood sheds). Both members of a breeding pair may fly toward several potential nest locations, then cling side by side at one particular site, with one member of the pair giving a rhythmic chipping call.

Behavior

Aerial Forager

Chimney Swifts spend their lives airborne, except when they are roosting or on the nest. They perform aerial courtship displays within 2 weeks of arriving on their North American breeding grounds, forming monogamous pairs for the season. In one of the best known displays, two birds fly close together, calling; first the rear bird and then the leader snaps its wings into a V-shape and the two glide together in a downward curve. Unmated birds roost together in large flocks, sometimes even in a chimney occupied by a nesting pair. Often an unmated helper may assist a breeding pair with rearing the young. After the young fledge, small groups of parents and young from several chimneys join larger staging flocks in bigger chimneys nearby. At the end of summer they gather into large groups to migrate to South America. During migration, as many as 10,000 swifts may circle in a tornado-like flock at dusk and funnel into a roosting chimney to spend the night. The lives of these widespread urban birds are surprisingly unstudied, because of their inaccessible nesting and roosting sites and their aerial lifestyle.

Conservation

Chimney Swifts have been in a long-term, rangewide decline of about 2.5% per year between 1966 and 2015, resulting in a cumulative decline of 72%, according to the North American Breeding Bird Survey. Partners in Flight estimates a global breeding population of 7.8 million, with 99% breeding in the U.S., and 1% in Canada. The 2014 State of the Birds Report listed the species as a Common Bird in Steep Decline. It rates a 12 out of 20 on the Continental Concern Score. Chimney Swift are not on the 2016 State of North America's Birds' Watch List. These birds probably became much more numerous with European settlement and the building of millions of chimneys. But traditional brick chimneys are now deteriorating and modern chimneys tend to be unsuitable for nest sites. Adding to the problem, some homeowners now cap their unused chimneys. Chimney cleaning during the nesting season can inadvertently destroy nests and kill swifts. Logging of old-growth forests can reduce the availability of natural nest sites. To prevent further decline, people may need to preserve existing chimneys or create new structures specifically for swift nesting; designs can be downloaded from the North American Chimney Swift Nest Site Research Project.

Migration

Long-distance migrant. Chimney Swifts migrate to South America each winter flying across the Gulf of Mexico or skirting it along the Texas coast (a route they’re more likely to take in spring than fall). Many swifts use one of three distinct flyways: the Atlantic coast, the east side of the Appalachians, and the Mississippi River. They fly high in the sky during the day and roost in chimneys at night.

Backyard Tips

Chimney Swifts may take up residence in your brick chimney if you leave the chimney cap off. It’s a good idea to keep the damper closed during summer and to schedule chimney cleanings either before or after the breeding season. If you don’t have a chimney, you can build a swift nesting tower with plans from the North American Chimney Swift Nest Site Research Project.

Find This Bird

The “flying cigar” silhouette of the Chimney Swift is a common sight all summer in the skies over eastern cities and towns. Lakes and rivers are especially good places to look for swifts, where they often forage along with swallows, which have broader wings and more fluid wingbeats. Be sure to keep an ear out for their distinctive, high-pitched chattering calls—they often call on the wing while foraging. During migration, thousands of swifts roost together in chimneys, funneling into them at dusk in spectacular tornado-like flocks.